Submarine groundwater discharge around Taiwan

A preliminary study shows that the submarine groundwater discharge (SGD) exists around Taiwan even though groundwater overdrawing on the island is serious. Fifteen of the 20 sites studied for major anions and cations recorded a clear SGD signal with freshwater outflow. A total of 278 salinity and major ion measurements were made. Sixteen nearly freshwater SGD (salinity⩽1.0) samples were obtained, providing strong and direct evidence for the existence of fresh meteoric groundwater entering the ocean from Taiwan. The total SGD flux is estimated to be 1.07×10¹⁰ t/a which is about 14% of the annual river output. The freshwater component of the SGD is 3.85×10⁹ t which is about 5.2% of the annual river discharge in Taiwan. The collected SGD has a composition similar to seawater with an addition of Ca, CO₃ and HCO₃ due to dissolution of calcareous rocks. Some samples with high Cl/(Na+K) may indicate pollution.